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Do You Get Exhausted During the Day? The Vitamin That Might Be to Blame

Are you yawning while reading this? (I'm not offended--I'm yawning, too. In my case, it was because I had three deadlines that all converged at once, so I stayed up way, way too late. All-nighters should disappear when you graduate from college. Hm, maybe they do for most people.)

But there are other reasons you may feel like nodding off way before bedtime, and a new study is suggesting that vitamin D may be one of them. But it's complicated.

A small study in the Journal of Clinical Sleep Medicine found that lack of vitamin D was found to have a direct association with how sleepy study participants were during the day--unless the participants were African-American, in which case more vitamin D was linked with daytime sleepiness. Researchers speculate that pigmentation found in different races may play a role in how vitamin D affects sleep, but say there's a lot more study needed (the research was also performed on study subjects who were eventually diagnosed with sleep disorders).